The present invention is related to systems and methods for charging batteries, and more particularly to systems and methods for switching between current and voltage mode charging.
The need for rechargeable batteries has increased in recent years due to the proliferation of portable electronics devices. A typical consumer electronics device includes a rechargeable battery and an associated battery charger. One complaint about such devices is that recharging the battery requires a significant amount of time. To address this complaint, fast charging approaches have been developed. For example, one common method of fast charging includes a fast charge portion where the battery is charged at a fast rate with a relatively high constant current followed by a slow charge portion where a low current derived from a constant voltage is used to charge the battery. Using this approach, the battery is charged using the high fixed current for a fixed period of time allowing the battery to charge at a relatively constant and fast rate. When the battery voltage nears its final value, the charging switches from a constant current mode to a constant voltage mode. While charging in the constant voltage mode, only a trickle current is applied to the battery. The switch from constant current mode to constant voltage mode is critical. In particular, if the switch occurs too late, the battery may overcharge and/or overheat.
In some cases, use of sensors has been proposed to detect when the battery voltage is approaching its final voltage. When a threshold near the final voltage is detected by the sensor, charging is switched from the constant current mode to the constant voltage mode. After the switch, a timer is initiated and based on predetermined battery profiles, the constant voltage mode charging is switched off after a period of time. However, the aforementioned method of switching between the constant current mode and constant voltage modes is not seamless and relies on predetermined battery characteristics.
Hence, for at least one or more of the aforementioned reasons, advanced systems and methods for battery charging are desired.